Manually merging https://trac.macports.org/changeset/24968: Use the mprsyncup strategy of pulling base/ from the RELEASE_URL.
Manually merging https://trac.macports.org/changeset/24968: Use the mprsyncup strategy of pulling base/ from the RELEASE_URL.

git-svn-id: dc463f922b716f8a7bf91846309830e794c23801@24974 d073be05-634f-4543-b044-5fe20cf6d1d6

danchr/macports-base,danchr/macports-base,neverpanic/macports-base,neverpanic/macports-base,macports/macports-base,macports/macports-base